Shunt for a web divided into several sectional webs

ABSTRACT

A shunt for a web, in particular a web of corrugated board, which is to be divided into several sectional webs in the conveying direction, comprises several shunting elements which are disposed side by side below the web of corrugated board and which are individually movable at least into a top position and a bottom position. Several compressed-air nozzles are provided, which are disposed above the shunting elements and directed towards the shunting elements and which are individually actuated by compressed air.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a shunt for a web, in particular a web ofcorrugated board, which is to be divided into several sectional webs inthe conveying direction.

2. Background Art

Shunts, i.e. switches, of the generic type comprise several shuntingelements crosswise of the conveying direction; these shunting elementsare arranged side by side below the web and are individually movableinto at least one top and bottom position of shunt. Adjusting drives areprovided for these motions to be carried out; they move the individualshunting elements from one position of shunt into another. Shunts, orswitches, of the generic type are provided in machines for treating, inparticular dividing, webs, in particular webs of corrugated board; thesectional webs, mostly in the number of two, are fed to a cross cutterwhere the sectional webs are cut into individual sheets, so-calledblanks, and deposited. The individual cross cutters of such across-cutter arrangement are disposed one on top of the other. Duringcontinuous conveyance of the sectional webs, the shunting elements thatare allocated to a top sectional web are in their top position of shunt,whereas the shunting elements that are allocated to a bottom sectionalweb are in their bottom position of shunt. Upon change of format i.e., achange in the width of the sectional webs, the entire web is being cutthrough crosswise and the leading sectional webs are run at a higherspeed, producing a gap between the leading sectional webs and thelagging sectional webs. When the gap between these sectional webs is inthe vicinity of the shunt, the shunting elements are set for correctallocation in width to the lagging sectional webs. For the sectionalwebs to be kept on the shunting elements, it has been known, over thetotal width of the web, to provide a pipe with a plurality of downwardoutlets, compressed air being blown through this pipe. Strong swirls ofair occur in particular when the lagging sectional webs enter the shunt,which may result in the sectional webs not being led accurately on theirway to the cross cutters of the cross-cutter arrangement. Experience hasin particular shown that an air jet is reflected by the bottom sectionalweb, lifting the top sectional web off the shunting elements so that itrises. The higher the velocity of the web, the more grows this problem.These web velocities can be higher than 300 m/min.

SUMMARY OF THE INVENTION

It is an object of the invention to embody a shunt of the generic typein such a way that reliable guidance of the lagging sectional webs isensured upon change of format.

According to the invention, this object is attained in a shunt,comprising a plurality of shunting elements, which are disposed side byside below the web of corrugated board, and which are individuallymovable at least into a top position and a bottom position; an adjustingdrive which acts on each shunting element, moving each shunting elementbetween the positions; and several compressed-air nozzles which aredisposed above the shunting elements and directed towards the shuntingelements, the nozzles being individually actuatable by compressed air.The gist of the invention resides in that several compressed-air nozzlesare provided over the width of a web; they can be triggered individuallyso that the sectional webs are kept reliably on the shunting elementsthat lead them, in particular directly after a change of format.Triggering the compressed-air nozzles can be handled appropriately: itis for example conceivable not to actuate the compressed-air nozzlesthat directly adjoin the longitudinal cut between the lagging sectionalwebs so that compressed-air swirls are precluded. The object accordingto the invention can be attained by special advantage in keeping with anembodiment wherein the compressed-air nozzles are individuallyactuatable by compressed air from a valve unit which is triggered by acontrol unit. Another advantage is offered when one or severalcompressed-air nozzles are provided above each shunting element.

Further advantageous embodiments consist in each compressed-air nozzlebeing disposed centrally above a shunting element; and in eachcompressed-air nozzle being disposed closely above a shunting element inthe top position thereof.

Use can be made of the solution according to the invention not only whena web is cut through entirely upon a change of format with the leadingsectional webs running at a higher speed, but by advantage even in caseof so-called gapless changes of format with only partial cross cutsbeing made.

Further features, advantages and details of the invention will becomeapparent from the ensuing description of an exemplary embodiment, takenin conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side view of part of a corrugating machine, including ashunt according to the invention;

FIG. 2 is a plan view of the machine according to FIG. 1; and

FIG. 3 is a view of details of FIG. 1 on an enlarged scale.

DESCRIPTION OF A PREFERRED EMBODIMENT

Seen in the conveying direction 1 of a web of corrugated board 2, thepart of a corrugating machine illustrated in the drawing successivelycomprises a short cross cutter 3, a corrugating unit 4, a longitudinalcutter 5, a shunt 6 and a duplex cross cutter 7. A transfer table 8 isprovided between the longitudinal cutter 5 and the shunt 6. Two tables,one on top of the other, are provided between the shunt 6 and the duplexcross cutter 7, a top table 9 of which leading to the top cross cutter10 of the duplex cross cutter 7 and a bottom table 11 leading to thebottom cross cutter 12 of the duplex cross cutter 7. The shunt 6includes shunting elements 13 of the type of so-called blades. Theseblades 13 are comprised of parallel, side by side bars of a width of forinstance approximately 10 cm crosswise of the conveying direction 1,which are pivoted about a joint pivoting axis 14 that is located invicinity to the table 8. By means of a linear drive, for example apneumatically actuated piston-cylinder drive 15, each shunting element13 is pivoted between a bottom and top position, which is roughlyoutlined in FIGS. 1 and 3. In the shunted top position, the shuntingelements 13, when pivoted upwards, align with the top table 9, whereasthe corresponding shunting elements 13 align with the bottom table 11 inthe shunted bottom position.

As far as described, this part of the machine is known and generalpractice.

A compressed-air nozzle 16 is disposed above each shunting element 13;it is directed substantially vertically from above towards the shuntingelement 13. Related to a direction crosswise of the conveying direction1, the nozzles 16 are disposed centrally above the shunting elements 13.They are located in proximity to the free ends 17, turned towards thetables 9, 11, of the shunting elements 13.

Compressed air is admitted to each nozzle 16 by a valve unit 19 via asupply line 18 allocated to each nozzle. This valve unit 19 is suppliedwith compressed air by a central source 20 of compressed air and acompressed-air storage unit 21 that provides for constant air pressure.The valve unit 19 is triggered by a central control unit 22 that alsoserves for triggering the drives 15. A central valve unit 23 is disposedupstream of the drives 15, which is fed by the compressed-air source 20.

The mode of operation is as follows:

A web 2 a advances in the conveying direction 1 on the top table 9,approaching the top cross cutter 10 where it is divided into individualsheets and led to a deposit (not shown). Another sectional web 2 b islocated on the bottom table 111 and approaches the bottom cross cutter12 of the duplex cross cutter 7 where it is likewise cut into sheets anddeposited. The two sectional webs 2 a and 2 b had previously beenproduced from the web 2 by a longitudinal cut in the longitudinal cutter5.

Upon the change of format that is roughly outlined in the drawing, theweb has been cut crosswise by a cross cut referenced 24. The leadingsectional webs 2 a and 2 b are accelerated in the duplex cross cutter 7so that a gap 25 forms between the leading sectional webs 2 a and 2 band the lagging sectional webs 2 c and 2 d. The webs 2 c and 2 d aredivided by a longitudinal cut 26 which is displaced from the cut 24 ofthe two sectional webs 2 a and 2 b, which is the norm for a change offormat.

When the gap 25 between the sectional webs 2 a, 2 b on the one hand and2 c and 2 d on the other is located above the shunt 6, the shuntingelements 13 are pivoted by corresponding actuation of the drives 15 sothat the shunting elements 13 are pivoted upwards over the width of thesectional web 2 c which is thus piloted on to the top table 9, whereasthe shunting elements 13, which reach over the width of the sectionalweb 2 d, are in their bottom position so that the sectional web 2 d isled on to the bottom table 11. With compressed air being admitted, inparticular during this change of format, to the nozzles 16 which areallocated to the sectional web 2 d that must be piloted on to the bottomtable 11, this sectional web 2 d is reliably kept on the shuntingelements 13 in their downwards pivoted position and led on to the bottomtable 11 through the gap 27 between the top table 9 and the bottom table11. In like manner, during this change of format, compressed air can beadmitted to the compressed-air nozzles 16 that are allocated to the topsectional web 2 c, this reliably preventing the sectional web 2 c, whichis to be led to the top table 9, from lifting off the shunting elements13. It is also possible to leave one or two nozzles 16 unaffected in thevicinity of the longitudinal cut 26, thus avoiding any swirls of airalong this boundary between the two sectional webs 2 c, 2 d.

1. A shunt (6) for a web (2) of corrugated board, which is to be dividedinto several sectional webs (2 a, 2 b, 2 c, 2 d) in the conveyingdirection (1), comprising a plurality of shunting elements (13), whichare disposed side by side below the web (2) of corrugated board, andwhich are individually movable at least into a top position and a bottomposition; an adjusting drive (15) which acts on each shunting element(13), moving each shunting element (13) between the positions; andseveral compressed-air nozzles (16) which are disposed above theshunting elements (13) and directed towards the shunting elements (13),the nozzles (16) being individually actuatable by compressed air.
 2. Ashunt (6) according to claim 1, wherein the compressed-air nozzles (16)are individually actuatable by compressed air from a valve unit (19)which is triggered by a control unit (22).
 3. A shunt (6) according toclaim 1, wherein at least one compressed-air nozzle (16) is disposedabove each shunting element (13).
 4. A shunt (6) according to claim 1,wherein each compressed-air nozzle (16) is disposed centrally above ashunting element (13).
 5. A shunt (6) according to claim 1, wherein eachcompressed-air nozzle (16) is disposed closely above a shunting element(13) in the top position thereof.